Effects of paclobutrazol and plant spacing on growth, yield, and after effect on sprout development in seed potatoes (solanum tuberosum l.)
- Authors: Jokazi, Khuselo Bernad https://orcid.org/0000-0002-8620-9838
- Date: 2021-01
- Subjects: Potatoes , Plant regulators
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/21323 , vital:48406
- Description: Potato (Solanum tuberosum L.) is an herbaceous plant that belongs to the genus Solanum, in the Solanaceae family which is comprised of about 2 800 species (Sahair et al., 2018). Potato domestication can be traced back to the sixteenth century in the South American continent (Hawkes, 1978). The potato crop became a staple food for greater parts of the world towards the end of the seventeenth century. It is not clear when the crop was introduced to the African continent, although the literature indicates that it was grown in some parts of the continent by the late seventeenth century (Hawkes, 1978). Potato is a very bulky crop and is a source of high energy per given area of land (Tsegaw, 2005). Nutritionally, the crop is rich in carbohydrates and provides a considerable amount of protein, with a good balance of amino acids, vitamins (C, B6, and B1, folate), minerals (potassium, phosphorus, calcium, and magnesium), and the micronutrients iron and zinc. Potatoes are also a source of high dietary fiber, especially when eaten unpeeled. In addition, potatoes are rich in antioxidants, including polyphenols, vitamin C, carotenoids, and tocopherols (Bradshaw and Ramsay, 2009). Potatoes play a very important role in the global food system. It is South Africa’s most important vegetable crop (DAFF, 2012). Worldwide, it ranks fourth topmost important food crops following wheat, maize, and rice (Esmaielpour et al., 2011; Bradshaw and Ramsay, 2009), followed by barley (Allemann et al., 2003). South Africa is the 27th largest producer in the world and the 3rd largest producer in Africa after Egypt and Malawi (FAOSTAT, 2015). In the year 2014, potatoes were produced in 51 435 hectares of land, which yielded over 2 million tons (DAFF, 2015). This crop is produced in sixteen producing regions throughout South Africa with the Limpopo, Free State, Western Cape, Mpumalanga, KwaZulu-Natal, and Eastern Cape provinces being the leading regions (DAFF, 2015). Because of the different climatic regions in South Africa, potatoes are planted at different times of the year. As a result, the country enjoys fresh potatoes throughout the year (DAFF, 2014). According to the Potato Industry Research Strategy 2014-17 under Potato South Africa, the past few years have seen a decrease in the area of land under potato production, with an increase in the average yield per area. This yield increment can be accredited to an increase in the production under irrigation system, the use of improved cultivars and seed quality, and the application of research results (PSA, 2014). World potato production indicates that intensive cultivation has led to an increment of potato yields between 1960 and 1999, even though there was a reduction in the area planted with the crop (Fabeiro et al., 2001). However, there is a large gap between potential potato yield and actual yield per hectare. Research undoubtedly holds great potential for narrowing this gap. In order to do so, there is a need to understand the factors limiting potato yield. Temperature, plant spacing, and seed tuber quality are amongst the most significant factors affecting potato growth, yield, and quality. Potatoes are very adaptive; at present, they can be produced in different climatic regions. They are temperate crops, which prefer a cool and humid climate (Haverkort, 1990), but care should be taken to avoid high-stress periods such as temperature extremes. The optimum temperature for haulm growth and net photosynthesis is in the range between 15℃ and 25℃, and 20℃ is the optimum temperature for tuberization. Tuberization is inhibited by temperatures above 29℃, as the photoassimilate partitioning towards the tubers is decreased, leading to an increase in shoot growth (Gawronska et al., 1992). Plant spacing is usually determined by the target market and cultivar. , Thesis (MSc) -- Faculty of Science and Agriculture, 2021
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- Date Issued: 2021-01
Exploring the fertiliser potential of biosolids from algae integrated wastewater treatment systems
- Authors: Mlambo, Patricia Zanele
- Date: 2014
- Subjects: Sewage disposal plants , Sewage sludge as fertilizer , Algae -- Biotechnology , Sewage -- Purification -- Anaerobic treatment , Plant regulators , Biofertilizers , Microalgae -- Biotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5957 , http://hdl.handle.net/10962/d1013342
- Description: High rate algae oxidation ponds (HRAOP) for domestic wastewater treatment generate biosolids that are predominantly microalgae. Consequently, HRAOP biosolids are enriched with minerals, amino acids, nutrients and possibly contain plant growth regulator (PGR)-like substances, which makes HRAOP biosolids attractive as fertiliser or PGR. This study investigated HRAOP biosolids as a starting material for a natural, cost-effective and readily-available eco-friendly organic fertiliser and/or PGRs. Various HRAOP extract formulations were prepared and their effect on plant growth and development was evaluated using selected bioassays. Initial screening included assessing the effect on change in specific leaf area, radish cotyledon expansion as an indicator of PGR-like activity, and seed germination index (GI). More detailed studies on fertiliser efficacy and PGR-like activity utilised bean (Phaseolus vulgaris) and tomato (Solanum lycopersicum) plants. Combined effects of sonicated (S) and 40% v/v methanol (M) extract (5:1 SM) had impressive plant responses, comparable to Hoagland solution (HS). Other potentially fertiliser formulations included 0.5% M, 1% M, 2.5% S and 5% S formulations. The 5:1 SM and 5% S showed greater PGR-like activity, promoting cotyledon expansion by 459 ± 0.02% and 362 ± 0.01%, respectively. GI data showed that none of the formulations negatively impacted germination. Further investigation showed that the 5% S formulation increased leaf length, width and area by 6.69 ± 0.24, 6.21 ± 0.2 mm and 41.55 ± 0.2 mm². All formulated fertiliser extracts had no adverse effect on chlorophyll content and plant nutrient balance as indicated by C:N (8-10:1) ratio. In addition, plants appeared to actively mobilise nutrients to regions where needed as evidenced by a shift in shoot: root ratio depending on C, N and water availability. Furthermore, 5% S caused a 75% increase in tomato productivity and had no effect on bean productivity. Whereas, 5:1 SM and 1% M formulation improved bean pod production by 33.3% and 11%, respectively but did not affect tomato production. Harvest index (HI) however indicated a 3% reduction in tomato productivity with 5:1 SM and little or no enhancement in bean productivity with both 5:1 SM and 5% S treatments. Bean plants treated with 5:1 SM and 5% S produced larger fruits, which could be an indication of the presence of a PGR effect. Overall, HRAOP biosolids extracts prepared and investigated in this study demonstrated both fertiliser characteristics and PGR-like activity with performances comparable and in some cases exceeding that of commercial products. However additional research is needed to confirm presence of PGR-like activities and fertiliser efficacy.
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- Date Issued: 2014